Dental implants are used to secure a false tooth or for securing other dental items, such as bridges, in the oral cavity. The aim is to achieve a firm, durable, yet flexible, intra-oral connection to the jaw bone of screw-type or cylinder-type structures made of a biologically compatible material. Such implants are often made of titanium, an alloy thereof, and some have been sprayed with titanium or coated with hydroxyl apatite.
Various forms of dental implants are described in Israel Patents 92360, 92561 and 92564. These specifications do not relate to the problem of drilling an accurate preparatory hole for the insertion therein of the implant.
Briefly, dental implants are inserted in the jaw bone of a patient using the procedure described below:
1. Clinical and radiographic examination. PA0 2. Preparation of a stone model of the relevant existing structures. PA0 3. Preparation of a transparent acrylic stent for use in the mouth during surgery. PA0 4. Bone exposure by incision and dissection of soft tissues. PA0 5. Drilling the bone, using clear acrylic splint as an (imprecise) guide. PA0 6. Hole expansion by further drilling or dilation. PA0 7. Insertion of a screw or cylinder implant. PA0 8. Adding a cover screw or healing cap to the implant head. PA0 9. Stabilizing the tissues to either cover the implant, or to leave the implant cover flush with the gingival tissue. PA0 10. Osseointegration, which takes place naturally during the following 4-12 months. PA0 11. Implant re-exposure, if necessary, and subsequent construction of a dental prosthesis on the implant infrastructure.
When the bone is of small dimensions or is porous, special techniques are used which include bore expansion by hammering in a dilator, increasing bone dimensions by making a chisel fracture, and floor elevation of the maxillary sinus cavity (bone grafting) for increasing the available depth and/or increasing the width by onlay bone or bone-substitute grafting.
Drilling of the bone is carried out by one of the following known techniques: a) free-hand drilling; b) drilling through a prepared hole in a plastic matrix, or c) drilling through a smooth, non-threaded, cylindrical metal drill bush held in a plastic matrix.
The initial hole in the jaw bone must be drilled at the correct location, typically half-way between two existing teeth, at the correct angle in all directions, and to the required depth. A faulty drilling trajectory is very difficult to correct and can cause damage to nearby structures such as the inferior alveolar nerve; it can also cause pain to the patient and, in some cases, cause implant failures.
Free-hand drilling is a technique which is suitable only for the exceptionally skilled and experienced dental surgeon. There will be difficulties when the bone being drilled is not homogeneous, the drill will be deflected and a too-large diameter hole will result.
Technique b) and, to an even greater extent, technique c), greatly reduce the above-mentioned risks associated with free-hand drilling. However, where the guide bore is directly drilled in the plastic matrix as in technique b), play between the bore and the drill is likely to develop, resulting in imperfect results. This problem is overcome in technique c).
The use of a metal drill bush has long been known in production engineering, and standard sizes are commercially available `off the shelf`. [See Wilson, Handbook of Fixture Design, McGraw-Hill Publishers, pp. 15-20 (1962)]. In technique c), this time-tested method is adapted to dental requirements.
However, the non-threaded metal drill bush is difficult to remove from the stent if it needs to be removed and redirected in a corrected drilling axis; furthermore, it is not axially adjustable. Lack of axial adjustment is a disadvantage when drill stability needs improvement, such as when the inner extremity of the bush is spaced from the bone being drilled. In addition, there is no secure means for adding attachments to the bush, such attachments having many important uses, as will be explained further below.
It is therefore an object of the present invention to obviate the disadvantages of the prior art dental implant drilling devices, and to provide a drill guide which is readily removable and replaceable, and which can be prechecked for accuracy.
It is a further object of the present invention to provide a drill guide which is readily depth-adjustable.
It is a still further object of the present invention to provide means for the secure attachment to the drill guide of attachments such as a bush for drilling a pilot hole, holders and guides for dilators and chisel heads, a radiographic marker, a depth gauge, sinus lift attachments, and the like.
Further objects of the invention will become apparent from the following description.